1. Field of the Invention
Apparatuses, devices, and methods consistent with the present invention relate to apparatuses using waveguides, and, more specifically, to optical touch panels using waveguides.
2. Description of the Related Art
Recently, there has been growing interest among researchers and consumers in alternative input methods for industrial electronic monitors, televisions (TVs), computers, cellular phones, personal data assistants (PDAs), automated teller machines (ATMs), and many other electronic devices. Input methods such as keyboard, keypad, and mouse become less viable as electronic devices become smaller because of the relatively large amount of space required to implement a keyboard or to manipulate a mouse. Moreover, the keyboard, keypad, and mouse are mechanical devices that tend to break down when placed in harsh industrial environments.
As an alternative to the above-described input methods, touch screens and touch panels based on resistive and capacitive technologies have been proposed. However, touch panels based on resistive and capacitive technologies have disadvantages in that resistive and capacitive touch panels require thin coatings of transparent conducting oxide (TCO) which are easily mechanically damaged, interfere with the color purity of the screen, and decrease the brightness of the screen. Moreover, the sensors used in the resistive and capacitive touch panels are heavy and also prone to mechanical breakage.
Touch screens and touch panels based on glass substrates have also been proposed. However, glass substrate touch screens require a specially fitted frame for mounting sensors over a monitor or display. This frame adds weight, cost, and complexity to the touch screen. Moreover, glass substrate based touch screens must be manufactured from individual substrates of cut glass. Working with large sheets of cut glass requires considerable care and skill so as not to break the glass and thus decrease yields. Thus, the manufacturing process is both costly and time consuming.
Optical type touch panels and touch screens address some of the disadvantages noted above with the resistive and capacitive touch panels and the glass substrate based touch panels. Thus, there is an increasing demand for optical type touch screens for use in a wide range of applications. To this end, two types of optical touch panels have been proposed, one based on light emitting elements and the other based on waveguides.
For example, U.S. Pat. No. 6,597,508 describes a related art optical touch panel which uses light emitting elements. Light emitting elements and light receiving elements are arranged in an alternating pattern on two perpendicular sides of a position detecting surface. The light receiving elements are provided with hollow cylinders. Mirrors are provided on the other sides of the panel. Light is emitted from one of the light emitting elements, reflected by the mirror, and is then received by the two light receiving elements to either side of the light emitting element. The hollow cylinders provided with the light receiving elements block out light reflected off of an object in a detection field of the panel or light from other light emitting elements which are not located on either side of the light receiving element.
However, the related art panel of U.S. Pat. No. 6,597,508 has a number of disadvantages. First, this panel requires a large number of light emitting elements and light receiving elements. This increases the cost. Second, because the light emitting elements must be alternated with the light receiving elements in order to ensure adequate sensitivity, and thus detectability of an object, the panel resolution is very low. Additionally, the light emitting element and light receiving elements are prone to mechanical damage. Each damaged light emitting element or light receiving element reduces the sensitivity of the touch panel even further.
As another example, U.S. Pat. No. 6,351,260 describes a related art optical touch panel using waveguides. Transmission waveguide sections are provided on perpendicular sides of a touch panel. Reception waveguide sections are provided on sides opposite to the transmission waveguides. A light transmitter is provided at one end of each transmission waveguide section and a processing receiver at one end of each reception waveguide section. Each waveguide section has layers of waveguides, the layers being mechanically aligned and placed together using a layer of polyester and optical cement. Light is transmitted from the light transmitter, through the transmission waveguide section, across the touch panel, into the reception waveguide section and to the processing receiver.
However, the related art panel described in U.S. Pat. No. 6,597,508, while an improvement over the related art touch panel using light emitting elements, also has a number of disadvantages. First, in the case of multiple waveguide sections, two light transmitters and two processing receivers are required. This results in increased cost and the use of increased physical area for two light transmitters and two processing receivers. Second, the use of separate transmit and receive waveguide sections requires careful alignment of the transmitting and receiving waveguide sections so that the waveguides of the transmitting and receiving waveguide sections correspond to each other. This process is costly. This process is also complicated in that it requires an initialization process in order to determine which waveguides are incorrectly aligned. The misaligned individual waveguides must then be disconnected, disabled, or otherwise discounted in order to decrease false positive readings. Lastly, this alignment problem creates additional problems for panels operating in harsh environments. In harsh environments, such as those in which industrial electronic monitors are used, the related art touch panel is prone to being jostled, dropped, and being subjected to other such mechanical stresses. These stresses may increase misalignment of the waveguides and thus decrease the sensitivity and accuracy of the related art optical touch panel.